High speed ferrite core drivers for phased array radars



D. G. JETERVQJRH ETAL.

HIGH SPEED FERRITE CORE DRIVERS FOR PHASED ARRAY HADARS Filed July 16, 1968 Glitz/Ir INVENTORJ' DAV/Z7 6. dire? '12. $0:

United States Patent ABSTRACT OF THE DISCLOSURE A circuit for driving high speed ferrite cores in phased array radars including the use of PNPN diodes which are turned on by means of a negative pulse which is coupled to the anode of a standard diode whereby the triggering source sees as an input impedance a large value resistor in parallel with a back bias diode thereby reducing power requirements and increasing the turn-off and recovery time.

BACKGROUND OF THE INVENTION This invention relates generally to ferrite phase shift elements and more specifically to a switching circuit for ferrite phase shift elements that is capable of extremely high switching rates.

Phase array antennas provide a new degree of freedom in radar systems by making possible a high frequency electronic scan. This scan rate is limited by the data handling equipment in most cases. However, as the capabilities of this equipment have been extended, a new limitation has been revealed. This limitation is the driver circuitry necessary to control the state of the elements in the phase shift array. These drivers must be capable of individually switching any number of elements in the array within a short interpulse interval. This interpulse interval becomes increasingly short as the scan rate is increased. Efforts to design driver circuitry capable of the speed required in modern high speed systems have resulted in equipment of prohibitive size, cost, and complexity. Until a satisfactory solution to the driver problem is produced, the scan rates of practical phased array radar systems are essentially limited to frequencies considerably less than 1 mc.

Phase shift arrays using the ferrite phase shift technique can logically be divided into two areas. The first area is the RF circuitry including the ferrite device. This portion of the array must control the RF power to the radating elements in a predictable and efiicient manner. The second area and remainder of the array is composed of the ferrite switching circuitry. This invention discloses a unique switching circuit which is capable of latching or saturating the ferrite phase shift element in either of the two states at extremely high switching rates.

When utilizing a ferrite core, certain primary requirements are imposed on the driver circuit. Included is a requirement that the driver circuit have a to ampere pulse current capability and a 100 to 200 volt switching capability.

Similarly, as a result of its application to phased array radars, additional stringent requirements are imposed on the driver circuit. Some of these requirements are bidirectional switching; low cost, in view of the large number of drivers required; small size, and high speed.

SUMMARY OF THE INVENTION In order to control the beam emanating from a phased array radar antenna it is necessary to have available the maximum possible speed in switching between the radiating elements. The maximum speed with which the 3,525,877 Patented Aug. 25, 1970 ferrite can be switched from one state to the other and back is dependent upon the recovery time of the switching device. Although silicon controlled devices have been tried with limited success in the past, this invention utilizes PNPN diodes which have significantly shorter tumoff and recovery times than the aforementioned devices.

By utilizing the four-layer diodes, which operate in a manner similar to a silicon controlled rectifier, it is possible to trigger the element by anode-cathode over voltage rather than the conventional gate signal input. The short forward recovery time of the PNPN diode makes possible lower cycling times.

It is therefore an object of this invention to provide a new and improved ferrite core driver for phased array radar.

It is another object of this invention to provide a new and improved driver circuit having a 10 to 15 ampere pulse current capability.

It is a further object of this invention to provide a new and improved driver circuit having a 10 to 15 ampere pulse current capability.

It is a further object of this invention to provide a new and improved driver circuit having a to 200 volt switching capability.

It is still another object of this invention to provide a new and improved high speed bidirectional switching circuit.

It is still another object of this invention to provide a new and improved driver circuit which may be manufactured at low cost.

It is still another object of this invention to provide a new and improved circuit which is of small size.

It is still a further object of this invention to provide a low current ferrite core driver with high circuit efliciency.

It is still another object of this invention to provide a high speed ferrite core driver for phased array radar which is economical to produce and utilizes conventional, currently available components that lend themselves to standard mass production manufacturing techniques.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a hysteresis curve of the circuit disclosed herein;

FIG. 2 is a circuit diagram of the invention; and

'FIG. 3 is a representation of the current pulses through the ferrite core included in this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the hysteresis curve shows the ferrite to be in the 0 state until the trigger pulse enters the circuit thereby causing current to flow as shown at i until it reaches the 1 state where it remains constant. When it is desired to switch the ferrite back to the 0 state another negative pulse is injected allowing the current to flow as shown at i whereby the ferrite will return to the 0 state.

In FIG. 2. the circuit is illustrated wherein the ferrite 10 is assumed to be in the 0 state and the cathode of PNPN diode 1'2 is at ground. When the negative trigger pulse 14 enters, PNPN diode 12 breaks over, causing the current to flow in the direction shown by i thus charging the capacitor 16 to a positive voltage. This charging current causes the ferrite to switch from the 0 to the 1 state as shown in FIG. 1. The anode of the PNPN diode 18 is now at a positive voltage (+V) To return the ferrite to its original or 0 state a negative trigger pulse 20 is injected at the cathode of PNPN diode 18, breaking it over and allowing the capacitor 16 to discharge through the ferrite 10 and the PNPN diode 18 to ground as shown in FIG. 1 by i The discharge current switches the ferrite back to the state.

The clamping circuit 22 is a conventional circuit and is utilized to control the current flowing through the ferrite.

FIG. 3 is a curve of the current pulse through the ferrite core when the circuit of this invention is utilized. Each indice along the abscissa is equal to l microsecond while along the ordinate each indice represents 5 amperes. The curve shows then, that in a period of less than two microseconds, the current will range from a minus amperes to a plus twelve ampers. These results clearly indicate that the invention will meet the requirements of modern, high speed, phased array radars.

Although the invention has been described with reference to one embodiment, it will be understood to those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claims.

We claim:

1. A high speed ferrite core driver comprising: a first multiple-layer diode semiconductor device; a diode connected to said first multiple layer diode; a ferrite core connected to the diodes; and a capacitor serially connected to the core; means for allowing current to flow through said first multiple layer diode and charge said capacitor whereby a flux field is created in the ferrite core; a second multilayer diode operatively connected with the ferrite core; a diode serially connected between the second multilayer diode and ground; and means for allowing a current to flow through said second multilayer diode, thereby discharging the capacitor and causing the orientation of the flux field to be reversed.

2. A high speed ferrite core driver circuit according to claim 1 including: a clamping circuit disposed intermediate said ferrite core and said capacitor whereby the voltage in said capacitor is limited.

3. A high speed ferrite core driver circuit according to claim 1 wherein: the means for allowing the current to flow through the first multilayer diode is a negative pulse generating means.

4. A high speed ferrite core driver circuit according to claim 1 wherein: the means for allowing the current to flow through the second multilayer diode is anegative pulse generating means.

References Cited UNITED STATES PATENTS 3,193,693 7/1965 Daykin 307-88 3,221,176 11/1965 Fritz et al. 307 -88 STANLEY M. URYNOWICZ, JR., Primary Examiner US. Cl. XJR- 340-174 

